Don't get a tattoo. It's a nagging regret waiting to happen. I regret 3 out of 4 of my tats. Those aren't good stats. They could be much worse, but I still wish I didn't have them. The worst one was a result of going off my meds and driving past a tattoo shop balls deep in a manic episode and something just telling me "YOU NEED TO GET A PINK FLOYD TATTOO RIGHT NOW!" So I went in and got the Dark Side of the Moon album art on my arm. From behind, all you can see is the rainbow, so if you're walking behind me it looks like some dyke shit.
If you feel like doing something wild with your appearance dye your hair, get a piercing you can remove later on, fuck around with colored contacts or whatever. Tats are just too permanent and too damn expensive to remove.